The Peptide Biochemistry Core (Core B) has two main goals: 1) to generate and maintain primary phage display libraries as tools for the proposed studies, 2) to design and execute experiments to isolate and characterize function-blocking peptides against the target proteins under investigation. Distinct strategies will be applied to each specific application. For proteins that have already been cloned, recombinant proteins will be purified and immobilized on solid supports. These include ephrin-A1 (formerly B61) fused to human IgG (ephrin-A1/IgG) (Project 1), Fas ligand that is immuno-affinity purified from a producing cell line (Project 2), and EGF residue K652-A674 fused to GST (Project 5). Primary peptide phage display libraries will be selected on the recombinant proteins. Selected phage will be amplified and selected on the target protein again. Following such repeated, peptide coding sequences from phage capable of specifically binding to target proteins will be fused to GST or synthesize. They will be used to test for blocking Eph kinase signaling (Project 1), or Fas-Fas ligand mediated apoptosis (Project 2). In project 5, the peptide sequences themselves will be used to deduce proteins that interact with EGFR K652-A674. Since functional recombinant proteins are not available for ion channel ROMK1 (Project 3), we will express it on Sf9 and CHO-Lec-1. By altering phage selection on insect and mammalian cells overexpressing the channel the non-specific binding associated with total cell panning will be minimized. Peptides will be synthesized and characterized using the channel clamping systems.